The magnetic barkhausen effect

When the magnetization of a ferromagnet (in this paper “ferromagnet” will often include “fernmagnet”) is changed under the influence of an applied magnetic field, the magnetization, particularly in the vicinity of the coercive force, is not smooth function of the field but rather shows a structure composed of many individual steps. This structure is evidence of irreversible changes in magnetization and is known as the barkhausen effect. The effect was named after its discoverer who, in 1919, connected a coil surrounding a ferromagnet to a newly invented amplifier and listened to the output of the amplifier with earphones.1